1. Field of the Invention
The present invention relates to an axial flow pump provided integrally with a motor, as well as a fluid circulating apparatus provided with the axial flow pump.
2. Discussion of the Background
Heretofore there has been known a fluid circulating apparatus for use in floor heating in which the heat of fluid such as hot water is utilized to heat a floor. In the fluid circulating apparatus, fluid stored in a water tank is heated with a heater and the temperature of the fluid is kept constant, allowing the fluid to circulate along a flow path by means of a pump to warm up the floor.
As the pump used in such a fluid circulating apparatus there is known an axial flow pump integral with a motor wherein a flow path is formed in the interior of the motor comprising a stator and a rotor as principal components, and an axial flow blade is formed on the rotor.
In such an axial flow pump integral with a motor, winding on a stator core of the stator is energized to rotate the rotor, thereby causing the axial flow blade to rotate, and fluid is sucked in from a suction port and is discharged from a discharge port through the motor.
In the axial flow pump integral with a motor, the entire inner periphery surface of the stator and the interior thereof, together with the winding, are molded with an insulating resin to waterproof the stator.
When the motor of the axial flow pump integral with a motor is driven, heat is generated from the winding on the stator core.
If the heat generated from the motor can be transmitted to, for example, the fluid flowing through the interior of the fluid circulating apparatus, it is possible to diminish heating with the heater by an amount corresponding to the amount of heat generated from the motor.
Generally, in the conventional axial flow pump integral with a motor, the stator is waterproofed with resin or the like, as referred to above. The resin or the like is low in thermal conductivity, thus giving rise to the problem that the heat generated from the stator cannot sufficiently be transmitted to the fluid.
Therefore, in the case of the conventional axial flow pump integral with a motor, there is no idea of positively utilizing the heat generated from the winding. Besides, although heat is generated from the motor, the heat cannot be fully utilized in the fluid circulating apparatus.
Further, the thermal conductivity of resin is as low as about 0.2 W (m·k), so if the stator is molded with resin, the heat generated from the winding is hard to escape to the exterior. As a result, it is necessary to provide cooling means, such as cooling fan. Because components of the axial flow pump such as stator winding and stator core are deteriorated by the heat and their service life becomes shorter by the heat generated from the motor.